Fluorescent whitening agents



United tates FLUORESCENT WHITENING AGENTS No Drawing. Application March26, 1953, Serial No. 344,888

8 Claims. (Cl. 260304) This invention relates to the production of novelorganic compounds which are useful as whitening agents for fibrousmaterial, such as cellulosic fibers or nylon. It is an object of thisinvention to produce compounds of the above general nature, but whichare characterized further by bleach fastness and by correct shade offluorescence. Additional objects and achievements of this invention willappear as the description proceeds.

The art of whitening or brightening textile fiber and paper is ofrelatively recent development. It has been found that fibrous materialswhich normally have a dull, yellowish cast when in the white, unbleachedstate, become whiter and brighter if treated with agents which fluoresceunder ultraviolet light. Presumably the action of the ultraviolet rayspresent in ordinary daylight is suflicient to excite these agents uponthe fiber to emit fluorescence which overcomes the undesirable tinge ofcolor in the unbleached fiber. Best results are obtained when the shadeof fluorescence is complementary to that of the unbleached fiber, sothat the colors will cancel out each other. Since the most comonoff-white shade of unbleached cellulosic and nylon fibers is yellowish,the most desirable shade in a fluorescent is blue.

Another very important demand developed by the trade is bleach fastness.Inasmuch as the aforementioned fluorescent agents are generallyincorporated into soap and synthetic detergents, which are packaged andmarketed for household use, and inasmuch as in household practicelaundered articles are often subjected to bleaching with various agents,for instance hypochlorites, it is essential that the fluorescenttransferred from the detergent to the fiber shall not be removed ordestroyed by the action of bleach. Unfortunately, most of thefluorescent agents now on the market, and having the desirable blueshade, are weak in respect to this qualification of bleach resistance.

In addition to the above two primary qualifications, an agent for thepurposes of this invention should be capable of being synthesizedeconomically from readily available materials, and should havesufficient fluorescent power (often referred to as tinctorial strength)to give the desired effect at a minimum cost. It should also haveafiinity for nylon fiber and should be capable of being dispersedreadily in water in the concentrations that would normally be used inthe treatment of nylon or other fiber.

Now according to our invention new chemical compounds are synthesizedwhich satisfy to an excellent degree all the aforegoing qualifications.The novel compounds of this invention are aromatic triazoles which carryin their molecule at least one and not more than two sulfamyl radicalsof the group consisting of unsubtituted sulfamyl, monoalkyl sulfamyl anddialkyl sulfamyl (SO2NH2, SO2NHR and SO2NRR, respectively, R and R beingalkyl radicals of not more than 4 C-atoms each). They may be definedgenerally by the formula .l 1. l J

wherein R represents the radical of 2-phenyl benzothiazole or a homologthereof (e. g. the radicals obtaining ateht tion ortho to the aminogroup unsubstituted, but it may 2,700,043 Patented Jan. 18, 1955benzothiazole, dehydrothio-p-toluidine and dehydrothiom-xylidine), X isa sulfamyl radical as above defined, Y is a member of the groupconsisting of H, sulfo and sulfamyl, the members X and Y being attachedto homocyclic nuclei on opposite sides of the triazole ring.

These compounds may be synthesized by diazotizing a 2-p-aminophenylbenzothiazole compound of the group more fully defined below, couplingthe diazo compound (in acid medium) to an amino-naphthalene compound ofthe group more fully defined below; and converting the o-amino azo dyethus obtained into a triazole by oxidation in known manner, for instanceby heating in The 2-p-aminophenyl-benzothiazole compound may be selectedfrom the group consisting of Z- -aminophenylbenzothiazole itself,dehydrothio-p-toluidine, dehydrothio-m-xylidine, and their sulfo andsulfamyl derivatives of the group above defined. The amino-naphthalenecompound may be lor Z-naphthylamine having the posicarry in otherpositions a sulfo group or a sulfamyl radical as above defined. The twocomponents mentioned are chosen so that at least one of them has asulfamyl radical.

The requisite sulfamyl derivatives of the p-aminophenyl-benzothiazolecompound or of the amino-napthalene, may be prepared by firstacetylating the corresponding amino compound with acetic anhydride, toblock the amino group; then sulfonating the compound with chlorosulfonicacid to convert it into a sulfonyl chloride. The latter is then treatedwith the appropriate amine (ammonia, methylamine, ethylamine,dimethylamine, etc.) to obtain the sulfonamide. Finally, hydrolysis withhot hydrochloric acid regenerates the amino group and gives the desiredsulfonamide compound.

Without limiting this invention, the following examples are given toillustrate our preferred mode of operation. Parts mentioned are byweight.

Example 1 240 parts (1 mol) of dehydrothio-p-toluidine was diazotized at1015 C. in 2000 parts of dilute hydroby dropping off the NHz group from2-p-aminophenylchloric acid with an excess of nitrous acid to give aclear solution of the diazo compound. To this was added a solution of244 parts (1.1 mol) of 2-aminonaphthalene-6-sulfonamide in 1000 parts ofwater. The acidity was adjusted to slightly acid on Congo red paper bythe addition of sodium acetate, and the coupling proceeded rapidly.After stirring overnight at room temperature the product was isolated bymaking the solution alkaline to Clayton yellow with sodium hydroxide,heating to 80 C., filtering, and washing with water.

The o-aminoazo dye intermediate thus obtained was oxidized to thetriazole 1by refluxing for 3 hours with 500 parts .(2 mols) of cupricsulfate (CuSOrSHzO) in an excess of aqueous ammonia. The mixture wasmade acid to Congo red paper with hydrochloric acid and filtered hot.The solid product was slurried in water, vmade alkaline to Claytonyellow paper with sodium hydroxide, and treated with an excess (positivetest on fiavanthrone paper) of sodium hydrosulfite for 16 hrs. at 70 C.The slurry was then made acid with hydrochloric acid and filtered. Theproduct was crystallized from aqueous dimethyl formamide .and dried.

When applied from an aqueous bath to cotton or nylon at 33 p. p. m.(based on fabric), the product gave a .fabric which appearedconsiderably whiter in daylight than the untreated fabric. The atfinityfor cotton and nylon was about equal, with a somewhat lower afiinity forcellulose acetate.

Example 2 342 parts ,(1 mol) of dehydrothiop-toluidine sodium sulfonatewas dissolved in water. An excess of hydrochloric acid was added and theamine was diazotized at 10l5 C. in the usual manner by the addition ofsodium nitrite. The diazo was then coupled to2-aminonaphthalene-6-sulfonamide and the dye isolated in the same manneras Example 1.

The azo dye thus obtained was oxidized by refluxing with ammoniacalcupric sulfate as in Example 1. The alkaline reaction mass was filteredand the cake was slurried in water, made acid to Congo red paper withhydrochloric acid. This slurry was heated to 8090 C. to dissolve allcopper salts and filtered hot. The cake was washed with water untilacid-free and dried. The final product is believed to have the structureCotton cloth treated in water with 84 p. p. m. of this whitening .of the.cotton and nylon with a lesser whitening efiect on the acetate fabriExample 4 Example 5 3-1.9 parts (0.1 mol) of the sulfonamide of dehydro-0 thio-p-toluidine was diazotized at 0-5 C. in dilute hydrochloric acidand the resulting diazo was coupled with 15.7 parts (0.11 mol) ofZ-aminonaphthalene in the usual manner. The resulting dye was oxidizedto the triazole by refluxing for 4-0 hrs. with 50 parts of cupricsulfate (CuSO45I-IzO) dissolved in a mixture of 185 parts of pyridineand 125 parts of water. The oxidation product was precipitated bydrowning in 2000 parts of 10% sulfuric acid. The final product wasfiltered off, washed with water, dried and crystallized from ethyleneglycol monoethyl ether. It was a pale yellow powder, soluble inalcoholic solvents with bright blue fluorescence. This product, whenapplied on cotton and nylon, gives a very strong bluish fluorescence.

Example 6 31.9 parts (0.1 mol) of the sulfonamide ofdehydrothio-p-toluidine was diazotized at 05 C. in dilute hydrochloricacid and the resulting diazo was coupled 9 toZ-aminonaphthalene-6-sulfonic acid in the usual manner. The resultingdye was oxidized as described in Example 1. The oxidation mixture wasfiltered hot and the triazole isolated from the filtrate by salting outwith sodium chloride, filtering, washing the product with 10% NaClsolution and drying. It was a cream colored powder, soluble in waterwith bright bluish fluorescence. The end product is believed to have theformula compound fluoresced brightly in ultraviolet light and appearedmuch whiter in daylight than untreated cloth.

Example 3 334 parts (1. mol) of the N-methyl sulfonamide oi' SOzNHz Whenappliedto cotton, nylon and celluloseacetate fabti'cs at '80 p. p. m.this agent caused considerable This compound applied on cotton and nylongives very strong bluish fluorescence.

Similar compounds may be prepared by coupling the diazotizeddehydrothio-p-toluidine-sulfonic acid, -sulfonamide, or-N-alkyl-sulfonamides to naphthionic acid (1-aminonaphthalenet-sulfonicacid), to Laurents acid (l-aminonaphthalene-S-sulfonic acid), or to thecorrespending sulfonamide or N-alkylsulfonamides of these acids, e. g.1-aminonaphthalene4-N,N-dimethylsulfonamide or Z-aminonaphthaiene-S (or6)-N,Ndirnethylsulfonamide, and oxidizing the resulting o-arninoazo dyeas in the aforegoing examples. a

in place of dehydrothio-p-toluidine and the sulfonic acids andsulfonamides thereof named in the examples, other derivatives of thesame class may be used, for instance Z-(p-aniinophenyl)-6-methylbenzothiazole-7-N,N- dimethylsulfonamide; also, dehydrothio-m-xylidineand 2-(p-aminophenyl)-benzothiazole, as well as their sulfo and sulfamylderivatives may be used with similar results.

The sulfonic acid compounds given in the above examples have beenisolated as the sodium salts of the sulfonic acids. By using potassiumhydroxide and po tassium salts in lieu of sodium hydroxide and sodiumsalts, throughout, the products may be obtained as potassium sulfonates.Isolation as the free sulfonic acids can beeffected by acidificationof-the condensation mass,

and the products thus obtained may be reacted with ammonium hydroxide orany suitable organic or inorganic base, to yield the corresponding salt.

The novel compounds hereinabove described, have been subjected by us tovarious tests to determine their bleach fastness, light fastness andwash fastness and showed that the novel compounds compare favorably inrespect to these qualities with the best fluorescents which are now onthe market.

In addition to being applied to textile fibers directly from a dye bathor to paper stock by addition to the beater, our novel compounds may beincorporated into soap and synthetic detergents. They may also be usedfor various other purposes where fluorescence or absorption ofultraviolet light is desirable, for instance to achieve fluorescenteffects in costumes or stage settings, to achieve novel effects onphotographic paper, as ultraviolet filters when impregnated oncellulosic films which are used for wrapping materials, etc.

We claim as our invention:

1. An aromatic triazole compound of the general formula F l X-| N: J Y

wherein R represents the 4'-radical of a compound selected from thegroup consisting of Z-phenyl benzothiazole and its lower homologs, X isa sulfamyl radical of the group consisting of unsubstituted sulfamyl,lower monoalkyl sulfamyl and lower dialkyl sulfamyl, Y is a member ofthe group consisting of hydrogen, sulfo and sulfamyl, the members X andY being attached to homocyclic nuclei on opposite sides of the triazolering.

2. An aromatic triazole compound of the formula f i =Q wherein R is the4-radical of 2-phenyl-6-methyl-benzothiazole carrying anN-methyl-sulfonamide group in the benzo nucleus, while Q is the1,2-radical of naphthalene- 6-sulfonamide.

3. An aromatic triazole compound of the formula R-N-N wherein R is the4'-radical of 2-phenyl-6-methyl-benzothiazole carrying a sulfonamidegroup in the benzo nucleus, while Q is a naphthalene radical attached inthe l,2-positions.

4. An aromatic triazole compound of the formula R-N-lfil l=Q wherein Ris the 4'-radical of 2-phenyl-6-methyl-benzothiazole carrying anN-methyl-sulfonamide group in the benzo nucleus, while Q is the1,2-radical of naphthalene- 6-sulfonic acid. 4

5. An aromatic triazole compound of the formula RNN I II =Q wherein R isthe 4-radical of sulfonated 2-phenyl-6- methylbenzothiazole, while Q isthe 1,2-radical of naphthalene-6-sulfonamide.

6. An aromatic triazole compound of the formula fi N=Q wherein R is the4'-radical of 2-phenyl-6-methyl-benzothiazole, while Q is the1,2-radical of naphthalene-6-sulfonamide.

7. The process of producing a fluorescent agent of bluish fluorescence,which comprises diazotizing a paminophenyl-benzothiazole of the groupconsisting of paminophenyl-benzothiazole, its lower homologs, and itssulfo and sulfamyl derivatives, coupling the diazo compound thus formedto an aminonaphthalene of the group consisting of l-aminonaphthalene,Z-aminonaphthalene and their sulfo and sulfamyl derivatives which arenot substituted in position ortho to the amino group, the selection ofsaid components from said groups being such that the resultingortho-aminoazo compound will possess at least one sulfamyl radical, andthen oxidizing said1 ortho-aminoazo compound to the corresponding triazoe.

8. A process as in claim 7, the oxidation being effected by heating thecompound in an aqueous solution of ammoniacal cupric sulfate.

References Cited in the file of this patent UNITED STATES PATENTS2,410,619 Allen et al. Nov. 5, 1946

1. AN AROMATIC TRIAZOLE COMPOUND OF THE GENERAL FORMULA